Compact rotary hammer



Ailg- 1965 G. w. MOCARTY ETAL 3,

COMPACT ROTARY HAMMER Filed June 27, 1963 mm m.

INVENTOR GEORGE W. MCCARTY HAROLD 0. SHORT ATTORNEY United States Patent3,23,490 CUMPACT ROTARY HAMMER George "W. McCarty and Hamid 0. Short,Towson, Md.,

assignors to The Blach and Decker Manufacturing Company, Towson, Md acorporation of Maryland Filed June 27, 1963, Ser. No. 291,0tl0 1filairn. (Cl. 173-109) The present invention relates to a compact rotaryhammer, and more particularly, to a portable electric hammer or similarpower-operated device, wherein a rotation of the tool is facilitatedtogether with a simultaneous impacting against the end of the toolshank.

It is an object of the present invention to provide a compact rotaryhammer wherein both ends of the motor shaft are utilized, one end todrive the percussive mechanism, and the other end to drive the mechanismwhich rotates the tool.

It is another object of the present invention to provide a portableelectric hammer, suitable for masonry drilling, concrete slotting, woodgouging, and for general demolition work, wherein the hammer is compact,considerably shorter than prior art devices, relatively lightweight, andconvenient for the operator to use.

It is yet another object of the present invention to provide a compactrotary hammer which uses readily-available components and is easy toassemble and economical to produce, yet out-performs competitive devicesand is rugged and reliable for continuous service over extended periodsof time.

In accordance with the general teachings of the present invention, thereis herein illustrated and described, a compact rotary hammer comprisinga housing, one preferably including an end handle provided with atrigger-type of switch, and further comprising a motor energized throughthe switch and having a shaft journaled fore and aft in the housing. Afloating ram is guided for reciprocation within the housing to one sideof the motor and is disposed on an axis which is substantially parallelto the axis of the motor shaft; and means are provided, driven by theaft end of the motor shaft, to reciprocate the ram. The housing isprovided with means to receive the shank of a tool, the end of which isstruck repeatedly and directly by the ram; and means are furtherprovided, driven by the fore end of the motor shaft, to rotate the tool.

In accordance with the specific teachings of the present invention,there is herein illustrated and described, a compact rotary hammercomprising a housing and a motor having a shaft journaled in respectivebearings fore and aft in the housing. A floating ram is disposed withinthe housing directly above the motor and is guided for reciprocationalong an axis which is substantially parallel to the axis of the motorshaft. Means are provided to reciprocate the ram, including a crankshaft journaled in the housing anteriorly of the motor on an axis whichis transverse to the axis of the motor shaft, the crank shaft beingdriven by the aft end of the motor shaft. A gear or other rotatablemember is journaled in the forward portion of the housing; and the gearis provided with a socket formed therein to receive the shank of thetool, the end of which is struck repeatedly and directly by the ram. Thegear is constantly rotated through gearing driven by the fore end of themotor shaft; and preferably, but not necessarily, the shank formation ofthe particular tool bit determines the type of motion developed by thehammer, namely, hammering only, rotation only, or a combination of bothhammering and rotation.

These and other objects of the present invention will become apparentfrom a reading of the following specifi cation, taken in conjunctionwith the enclosed drawings, in which:

FIGURE 1 is a side elevation of the compact rotary hammer of the presentinvention;

FIGURE 2 is an enlarged longitudinal section of the compact rotaryhammer; and

FIGURES 3a, 3b and 3c are views of the forward portion of the hammer andrespective tools used therewith, showing the development of bothhammering and rotation, pure rotation, and pure hammering, respectively.

With reference to FIGURES 1 and 2, the compact rotary hammer 10 of thepresent invention has a housing which comprises anend housing 11, amotor housing 12, a gear case 13 and a gear case cover 14-, and an endhandle 15, the latter being provided with a trigger switch 16 and aconventional line cord 17. As desired, each of the housing portions11-15 may be die-cast from a suitable aluminum alloy or may be moldedfrom a suitable glass fiber material.

With particular reference to FIGURE 2 the motor housing 12 has anelectric motor (or other power source) which is conventional andcomprises a pair of field windings 18 and a rotating armature 19. Thearmature 19 is provided with a motor shaft 20 which is journaled inrespective bearings 21 and 22 disposed fore and aft in the housing.Bearing 21 is retained within a boss 21a formed in the forward portionof the motor housing 12, while bearing 22 (on the aft end of the motorshaft 20) is retained within a boss 220: formed in the gear case cover14. A fan 23 is mounted upon the aft end of the motor shaft 20, and afan baffie 24 is disposed between the fan 23 and the motor for divertingthe cooling air through suitable openings 23a in a well-known manner.The bearing 22 is retained by means of a cone lock washer 25 and locknut 26 which engages the threaded portion 27' of the shaft 20, and also,by means of a retainer plate 28 which is secured to the gear case cover14 by a plurality of screws, one of which is shown in elevation as at29. A bevel pinion 34 is formed on the aft end of the motor shaft 20,and preferably but not necessarily, the pinion 30 is of the well-knownhypoid type gear for reasons of strength and compactness. The pinion 30is designed to engage a bevel gear 31 (of like formation) which has aloose splined connection 32 with respect to a crankshaft 33. Thecrankshaft 33 is disposed within the gear case 13 anteriorly of themotor and along an axis which is substantially transverse to the axis ofthe motor shaft 20. The crankshaft 33 is journaled in a ball bearing 34and in a closed needle bearing 35, which are retained within respectivebosses 34a and 36 formed in the gear case 13. The bevel gear 31 issecured on the crankshaft 33 by means of a cone lock washer 37 and apair of locking nuts 38, the latter engaging respective threads 39formed on the crankshaft. The ball bearing 34 is retained by means of aretainer plate 40 which is secured to the gear case 13 by means of aplurality of screws, one of which is shown in section as at 41. Thecrankshaft 33 has an integral crank body 42 within which a crank pin 43is secured on an eccentric axis. A connecting rod 44 is mounted upon thecrank pin 43, and a sleeve bearing 45, preferably of the Graphmo type(manufactured and sold by Timken Roller Bearing Co.) is disposedtherebetween. If desired, the crank pin 43 and the connecting rod 44 maybe suitably lubricated, such as is illustrated and described in theco-pending Short application S.N. 218,678 filed August 23, 1963,entitled Lubricator for a Motion- Translating Mechanism, and assigned tothe assignee of the present invention. The other end of the connectingrod 44 is pivotably mounted to a reciprocating crosshead 46 through awrist pin 47, and the crosshead 46 is guided within a sleeve 48 which isretained within the motor housing 11. A tubular piston rod 49 is formedintegrally with the cross-head 46, and a relatively-short disc-shapedpiston 50 is formed integrally on the forward end of the piston rod 49.The piston 50 is disposed within a floating ram 51 which is guided onrails 52 within the sleeve 48. Preferably, the ram 51 is of the hollowcylindrical type, and a chamber 53 is formed between the piston 50 andthe ram 51 for trapping a quantity of air therein. The air entrapped inthe chamber 53 exhibits alternate compression and rarefaction effectsand thus comprises an air spring which has a two-fold purpose: one toadvance or accelerate the ram 51 ahead of the reciprocating piston 50 bymeans of a compression of the entrapped air, and secondly, to withdrawor retract the ram 51 within the sleeve 48 by means of a suction effectwhich may be aided by the rebound of the hammer blow struck by the ram.Some type of momentary venting means is provided for the entrapped airchamber 53 so that the mass of entrapped air may adjust itself to asubstantially constant working level during the operation of the tool,and a preferred embodiment of the momentary vending means comprises aninternal annular recess 54 formed within the ram 51, the recess having agreater axial width than the corresponding height of therelatively-short disc-shaped piston 50; consequently, the entrapped airchamber 53 communicates with the atmosphere whenever the piston 50passes by the internal annular recess 54 formed in the ram 51, it beingnoted that the piston 50 and ram 51 reciprocate (not in unison) butrelative to one another. Further details of the structure and operationof the momentary venting means, in particular, and of the reciprocatingpiston and ram in general, are described in the Akerman Patent 3,034,302issued May 15, 1962, entitled Momentary Venting Means for Power-OperatedPercussive Tool, and assigned to the assignee of the present invention.However, it will be understood by those skilled in the art that anysuitable means for reciprocating the floating ram 51 may be employed inconjunction with the teachings of the present invention. Moreover, anexternal annular groove 55 is formed on the piston 50, and a sealingring 56 is disposed within the annular groove 55; preferably, thesealing ring 56 has an axial clearance with respect to the width of thegroove 55, measured axially, and also has a radial clearance withrespect to the inner diameter of the piston measured at the trough ofthe annular groove 55, such that the sealing ring 56 has a loose fitwith respect to the piston 50. The concurrent usage of the loose-fittingsealing ring 56 further enhances the cycling and smooth operation of thetool, as described more particularly in the Atkinson Patent 3,067,584issued on December 11, 1962, entitled Sealing Ring Means forReciprocating Piston Used in Power- Operated Percussion Tool, andassigned to the assignee of the present invention. Furthermore, theforward portion of the piston 50 is provided with a cylindricalprotrusion 57 which is designed (at times) to cooperate with acylindrical recess 58 formed in the closed forward portion of the ram51. At certain times over the extended life of the mechanism, moreparticularly when the sealing ring 56 has become somewhat deteriorated,the piston 50 may tend to bottom or impact against the closed end of theram 51; and in order to preclude a continuous impacting or bottoming ofthe piston 50, the protrusion 57 is received within the recess 58 andacquires a press-fit therein, such that the floating ram 51 is caught bythe reciprocating piston 50 and further impacting therebetween isprecluded. Further details of this particular structure and is mode ofoperation may be obtained in the Atkinson Patent 3,032,998 issued on May8, 1962, entitled Ram Catcher for Piston-Ram Assembly, and assigned tothe assignee of the present invention. However, it will be appreciatedby those skilled in the art that any suitable type of power-operatedmeans may be employed to reciprocate the ram 51 insofar as the meansemployed is driven by the aft end of the motor shaft 20 in accordancewith the teachings of the present invention.

With further reference to FIGURE 2, a nose piece comprising a flangedbushing 59 is secured to the forward portion of the motor housing 11 bymeans of a plurality of screws 60 and respective lock washer 61, thescrews being received within corresponding threaded recesses 62 formedin the housing, and a cone lock washer 63 being disposed between theflanged portion of the nose piece 59 and the motor housing 12. Betweenthe nose piece 59 and the end of the sleeve 48, there is disposed anO-ring 64, a bumper plate comprising a ring 65, and a split-collet 66,the purpose of which is to prevent the ram 51 from impacting against thenose piece 59 and the adjacent elements of the mechanism. A hearingsleeve 67 is pressed within the nose piece 59 so as to journal theintegral tubular neck portion 68 of a gear 69 or other rotatable member.A washer 70 is disposed between the bearing sleeve 67 and the real faceof the gear 69. The forward face of the gear 69 engages a bearingbushing 71 which is pressed within the end housing 11. The gear 69 isdriven by a pinion 72 which is formed on a jack shaft 73, and the jackshaft 73 is journaled (below the longitudinal midplane of the tool asviewed in FIGURE 2) within respective closed needle bearings 74 and 75fore and aft in the housing. The bearing 74 is retained within a boss 76formed in the end housing 11 while the other bearing 75 is retainedwithin a boss 77 formed in the motor housing 12. A pair of thrustwashers 78 are mounted on the jack shaft 73 adjacent the bearings 74 and75, respectively, and the jack shaft carriers an intermediate gear 79.The gear 79 engages a pinion 80 which is loosely mounted on the fore endof the motor shaft 20. The fore end of the shaft 20 carries a pair ofkeyed washers 32, a pair of thrust washers 83, and a pair of cone lockwashers 84, all of which are retained by means of a lock nut engagingthe threaded portion 86 of the shaft 20, thereby forming afriction-actuated slip clutch between the pinion 80 and the motor shaft20. The extreme forward portion of the motor shaft 20 is provided with ahexagonal socket 87, and a removable cap plug 88 is carried by the endhousing 11 forwardly of the shaft 20. Consequently, the plug 88 may beremoved, and a pair of suitable wrenches applied, one to the hexagonalsocket 87 and the other to the nut 85, so as to adjust the degree oftorque at which the clutch will slip to a predetermined level. Thestructural details of the slip clutch and its mode of operation, as wellas the nature and purpose of the rotating gear 69, are provided in thecopending Short application S.N. 213,363, filed July 30, 1962, entitledRotary Hammer, and assigned to the assignee of the present invention. Acommutator 89 is carried by the armature 19, and a collar 89a isdisposed between the commutator 89 and the bearing 21. The commutator 89engages suitable electrical brushes mounted in the forward portion ofthe tool housing in respective brush holder, one of which is shown as at101 in FIGURE 1; the manner of bringing the electrical wires from thecord 17 into the end handle 15 and through the motor housing 12 to thebrushes which engage the commutator 89, form no part of the presentinvention and hence are omitted herein for ease of illustration.

With reference again to FIGURE 2, and with further reference to FIGURES3a, 3b, and 3c, the application and inherent utility of the presentinvention may be described with reference to a number of conventionaltools, each of which is readily available in the commercial market. Asshown in FIGURE 2, the structure of the compact rotary hammer 10includes the rotating gear 69 which (together with its integral neckportion 68) is provided with a round axial bore 90, a counterbore 91,and a hexagonal (or other polygonal) socket 92. In FIGURE 3a, aconventional tool 93 (preferably of the carbide type) is inserted withinthe hammer 10, such that the hexagonal shank portion 94 of the tool 93is received within the socket 92 of the gear 69, and such that the endof the shank will be repeatedly struck by the ram 51. Consequently, botha hammering and a simultaneous rotation is obtained. In FIGURE 3b,another standard tool 95 is inserted within the hammer 10, and the tool95 (which again may be of the carbide type) is similar to the tool 93but has a shorter hexagonal shank portion 96 than that of the tool 93.Consequently, the tool 95 is continuously rotated, but being shorter, isnot engaged by the impacting ram 51; and thus a pure rotation isobtained without any hammering action. Each of the tools 93 and 95 areused primarily for drilling in masonry, such as concrete, or for similaroperations. In FIGURE 3c, still another standard tool 97 (referred to inthe art as a bull point and used primarily for demolition work) isinserted within the hammer 10, and the tool 97 has a round shank portion98 which is received loosely within the hexagonal socket 92 and which issufficiently long so as to be struck by the ram 51. Consequently, a purehammering or percussive action is obtained without any simultaneousrotation of the tool; and indeed, rotation is altogether precluded bymeans of the hexagonal shank portion 99 of the tool 97, which isreceived within the hexagonal socket 100 formed within the stationarybearing bushing 71. Consequently, it will be appreciated that the typeof motion desired by the user, namely, pure hammering, pure rotation, ora combination of both hammering and rotation, may be obtained by use ofthe proper type of conventional tool, and more particularly, the shankformation thereof; and further details on the particular structure ofthe tools and their mode of operation, which are well-known in the art,are given in the aforesaid Short co-pending application.

The compactness of the rotary hammer of the present invention isachieved first, by having the motor beneath (or above or to one side of)the reciprocating ram 51, and secondly, by using both ends of the motorshaft 20, the aft end driving the crankshaft 33 and other elements ofthe percussive mechanism, and the fore end driving the gear 69 and otherelements of the rotary mechanism. This structural arrangement results ina considerably shorter tool than competitive prior art devices, yetstill retains the desirable features of striking a very hard blow and(at the same time) rotating the shank of the tool.

Obviously, many modifications may be made without departing from thebasic spirit of the present invention; and accordingly, within the scopeof the appended claim, the invention may be practiced other than as hasbeen specifically described herein.

We claim:

A compact rotary-hammer tool, comprising:

(a) a housing having a rearwardly-disposed end handle provided with atrigger-type of switch for manually actuating the tool;

(b) an electric motor in the housing connected to said switch;

(c) said motor including an armature having an armature shaft journaledin bearings forwardly and rearwardly in said housing; the rearwardportion of said armature shaft being of larger diameter than the forwardportion, and the respective bearing for said rearward portion beingcorrespondingly larger than the respective forward bearing;

(d) a commutator carried on the forward portion of said armature shaftbetween said armature and the respective forward bearing for thearmature shaft, and electrical brushes mounted in the forward portion ofsaid housing for engaging said commutator;

(e) said housing having a longitudinal barrel parallel to said motor andspaced laterally therefrom, and said barrel having a floating ram guidedfor reciprocation therein;

(f) means including a reciprocating mechanism and a vertically-journaledcrankshaft driven by the rearward end of said armature shaft, throughcooperating bevel gears, one gear on said rearward end of said armatureshaft, and the other gear on said crankshaft, for reciprocating saidram, whereby the larger diameter rearward bearing for the armature shaftaccommodates the relatively-higher mechanical loads occasioned by thecrankshaft and the reciprocating mechanism;

(g) a gear journaled for rotation in the housing forwardly of saidbarrel; said gear having integral socket means formed therein forreceiving the shank of a tool bit, the end of which is struck repeatedlyand directly by said ram;

(h) gearing means driven by the forwardmost end of said armature shaft,forwardly of the respective forward bearing for the armature shaft, fordriving said gear; and

(i) a torque-responsive slip clutch means in said gearing means.

References Cited by the Examiner UNITED STATES PATENTS BROUGHTON G.DURHAM, Primary Examiner.

